This communication reports novel geochemical and geochronological data of granite from the southeastern part of the Bastar Craton, Central India. The studied samples are leucocratic in appearance and composed of quartz, K-feldspar, plagioclase feldspar, and biotite in decreasing order of abundances. Apatite, sphene, and zircon occur as accessory minerals. The SiO2 and Al2O3 content of the studied sample varies between 61 and 69 wt.% and 13 and 15 wt.%, respectively. The alkali oxides, K2O, and Na2O content ranges between 3 and 6 wt.% and 2 and 3 wt. %, respectively. In the primitive mantle normalized spider diagram, the granites exhibit a negative Nb–Ti, Sr anomaly, and a positive Pb–Th anomaly. Similarly, in the REE normalized spider plot, the granites exhibit a strongly fractionated trend La/YbCN=10.90−28.4 with a negative Eu anomaly (0.42-0.70). The zircon saturation in silicate melt yields crystallization temperature (Tzr) ~650 to 800°C for the Eastern Bastar Craton rocks. The P-T pseudosection modeling implies EBC granites which are crystallized at 700-750°C, at 0.4 to 0.6 GPa. The SHRIMP U-Pb ages from magmatic zircon yield an upper intercept at ~2470 Ma and a lower intercept at ~2100 Ma. When combined with the results of P-T pseudosection modeling, the geochemical and geochronological data classifies the Eastern Bastar Craton rocks as A2 granites that were emplaced during the amalgamation of Archean blocks leading to extended Ur formation. The ~2100 Ma age is correlated with mafic dyke emplacement and the Bastar Craton–Yilgarn Craton block disintegration before Paleoproterozoic Columbia supercontinent assembly.
<p>The Pakhal basin occurs as two parallel NW-SE trending sub-basins (Western and Eastern) located at the East-Dharwar Craton (EDC) and the Bastar Craton junction. The metasedimentary rocks exposed at the western side of the basin are known as the Pakhal belt, whereas those exposed on the eastern sides are known as the Albaka belt. The aggregate thickness of the sediments is nearly 6000 meters. Researchers have studied the geochemical affinities of Pakhal and Albaka rock, which proved to be crucial to understand the basin-architecture, source of sediments, and basin evolution in the context of rifting of the Dharwar and the Bastar craton However, the timing of inversion of tectonics and subsequent basin convergence is not studied.</p><p>Xenoliths of metasedimentary rocks are exposed within the EDC granites near the Pakhal basin. Aggregates of biotite, muscovite, plagioclase, and quartz constitute these metasedimentary rocks. Monazite, zircon, and iron-oxide are present as accessory minerals. The X<sub>Mg</sub> Biotite (22 Opfu) varies from 0.86-0.10 and Ti content of biotite varies between 0.26-0.34 apfu. The mica is mostly muscovite with mean Si (22 Opfu.) content of 6.28 apfu. The X<sub>Ab</sub> of plagioclase is constrained to be 0.97 apfu. The P-T conditions of metasedimentary xenoliths are constrained by using conventional geothermobarometers and P-T pseudosection analysis. The Ti content in biotite yield peak temperature 650<sup>0</sup>C for the stabilization of biotite. The P-T pseudosection analysis and subsequent modeling of compositional parameters imply a temperature window of 600-700 <sup>0</sup>C and pressure 0.6-1.0 GPa for the stability of biotite-muscovite-plagioclase-quartz assemblages. ~ 50 &#956;m monazites grains are dispersed throughout the studied sample. The ThO<sub>2</sub> content in the monazite grains varies between 1.7-5.8 wt%. Compositionally, the monazite grains are mostly La-Ce-Nd monazite in a tripartite classification. In a histogram distribution, the U-Th-Pb total spot ages exhibit two prominent peaks, at ~ 1295 Ma and ~ 1111 Ma. When combined with the P-T pseudosection analysis, the monazite ages imply rifting and opening the basin at ~ 1295 Ma. The ~ 1111 Ma monazite growth is correlated with granite emplacement and amalgamation of the Dharwar and the Bastar craton during Neoproterozoic Rodinia assembly.</p>
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